This invention relates to a gas seal control system and method for a gas compressor, and, more particularly, to such a system and method according to which a seal gas is applied to a gas seal in the compressor.
Gas compressors are well known, and include a housing for receiving a product gas to be compressed, a shaft rotatably mounted in the housing, and an impeller fixed to the shaft and cooperating with stationary vanes for compressing the gas before the compressed gas is discharged from the housing.
In many of these arrangements, one or more gas seals are often provided around the shaft between the impeller and the respective ends of the shaft for minimizing leakage of the gas from the high pressure area. During operation of the compressor, at least a portion of the product gas from the compressor is introduced to the seals to maintain a high pressure sealing effect. However this product gas often contains foreign matter, such as dirt, iron filings, and other solid particles which can contaminate the seals. Therefore, a seal gas from an external source is sometimes introduced to the seals to prevent possible contamination of the seals. However, the external seal gas, which is usually nitrogen, is relatively expensive and must be stored and transported from the external source to the compressor, which further adds to the cost.
Therefore, what is needed is gas compressor in which relative clean seal gas can be applied to the seals without significantly adding to the cost.
According to the system and method of an embodiment of the present invention, a product gas is introduced into and compressed in, a compressor. A portion of the compressed gas is discharged to external equipment, and a portion of the gas is trapped in response to deactivation of the compressor. The trapped gas is passed back to the deactivated compressor and functions as a seal gas.
This embodiment enjoys the advantages of utilizing product gas as a seal gas to eliminate the costs associated with a separate seal gas.